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As newborns spend most of their time asleep, this newfound ability might be crucial to rapidly adapt to the world around them and help to ensure their survival, researchers said.

In experiments with 26 sleeping infants, each just one to two days old, scientists played a musical tone followed by a puff of air to their eyes 200 times over the course of a half-hour. A network of 124 electrodes stuckon the scalp and face of each baby also recorded brain activityduring the experiments.

The babies rapidly learned that they could expect a puff of air upon hearing the tone, showing a four-fold increase on average in the chances of tightening their eyelids in response to the sound by the end of each session.

"It's surprising how quickly they learned — the study took 30 minutes, but I think they actually learned this in half that time," said researcher William Fifer, a developmental neuroscientist at Columbia University in New York. "We knew that a baby's job is to be an information gatherer, a data sponge, but I don't think we realized this also happens when they're sound asleep."

Babies' brain activity grew
Certain aspects of brain-wave activity over the frontal parts of the babies' brains also increased significantly over time during the experiments. This potentially reflected how the newborns were updating their memories. In fact, past research showed that the brains of sleeping infantswere abuzz with activity in regions associated with visual, motor and auditory processing.

In the new study, the kind of learned response with their eyes depends on the part of the brain known as the cerebellum. In autism and dyslexia, there are abnormalities linked with the cerebellum, suggesting this kind of study may offer a new way to identify at-risk infants at a very early age.

"We don't have very good tools right now to assess brain function in very early infancy, so this could prove very useful in measuring how well the brain is developing," Fifer said. "And babies spend so much time asleep, which fortunately could be an ideal time and state to ask questions of their brain."

There are now a number of interesting questions that scientists can now pursue with this research. For instance, "if the babies learned something on day one while asleep, do they remember it on day two when they are awake, or has it come and gone?" Fifer wondered.

Fifer and his colleagues detailed their findings online May 17 in the Proceedings of the National Academy of Sciences.